A BBC filmmaker Martyn Stewart on his way to cover the bloody dolphin hunt in Taiji has been reportedly detained at Kansai airport, sparking an outcry and calls to free the journalist.

Martyn Stewart, who films documentaries about the annual cull in Taiji Cove, said he was locked up at Kansai airport in Osaka. He said he was being accused of being an “eco-terrorist” and the way he has been treated was “nothing short of criminal.”

“I am locked in a cell room at Osaka airport waiting on appeal to the high minister regarding my entry into Japan,” Stewart said on a post on his Facebook page.

Stewart has visited Japan several times to film the traditional dolphin hunt in Taiji, in which hundreds of cetaceans are coralled into a cove and slaughtered for their meat. Some are selected to be sold to aquariums.

Footage and photos of the gruesome hunt showed the waters stained red with the creatures’ blood. Local fishermen insisted the killing was “humane,” and that the dolphins “feel no pain” when slaughtered.

But outraged activists and citizens say there is more to the hunt that Japan doesn’t want the world to see and Stewart could expose all of that.

“My footage is not liked in Japan apparently,” he said.

“In four years of being here for the dolphins I have maintained the law and abided by their rules. My words and pictures did the rest.”

“The government of Japan will do anything to protect the rights of the fishermen of Taiji and the barbaric treatment of the animals involved.”

Following his post on Facebook, calls for Stewart’s release have reverberated throughout social media, with some urging US Ambassador Caroline Kennedy to take action.

Kennedy herself expressed disdain for the bloodbath. Taiji fishermen said Kennedy should see the hunt with her own eyes and how it keeps the local economy alive.